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At least 343 records · Page 19Linked to original sources

PubMed2005

New paradigms for supporting the resilience of marine ecosystems.

Resource managers and scientists from disparate disciplines are rising to the challenge of understanding and moderating human impacts on marine ecosystems. Traditional barriers to communication between marine ecologists, fisheries biologists, social scientists and economists are beginning to break down, and the distinction between applied and basic research is fading. These ongoing trends arise, in part, from an increasing awareness of the profound influence of people on the functioning of all marine ecosystems, an increased focus on spatial and temporal scale, and a renewed assessment of the role of biodiversity in the sustainability of ecosystem goods and services upon which human societies depend. Here, we highlight the emergence of a complex systems approach for sustaining and repairing marine ecosystems, linking ecological resilience to governance structures, economics and society.

Journal Article↗

PubMed2002

Application of an ecosystem model for aquatic ecological risk assessment of chemicals for a Japanese lake.

The Lake Suwa version of the comprehensive aquatic systems model (CASM-SUWA) was developed using field data from Lake Suwa and evaluated to examine the utility of CASM-SUWA for assessing the ecological risk of chemicals for aquatic ecosystems. The calibration of the parameters for the model provided that the established reference model simulation could reproduce complex seasonal biomass behavior of populations that were not significantly different from the general seasonal pattern for the Lake Suwa ecosystem. The sensitivity analyses revealed the potential importance of indirect effects and demonstrated that the parameter values of all the trophic levels were important in determining the biomass of each trophic level in the model. The risk estimation of linear alkylbenzene sulfonates (LAS) demonstrated that the model estimated the risks of direct toxic effects on each population and the indirect ecological effects that propagate through the food-web in the model ecosystem. The CASM-SUWA-derived benchmark levels were approximately one order of magnitude less than the field-derived NOECs in literature. The analyses of the comparison implied that the model could provide a good basis in determining an ecological protective level of a chemical of concern in aquatic ecosystem. This modeling study demonstrated that the model can be used to provide additional information for the decision-making process in the management of the aquatic ecological risk of chemicals.

Benchmarking↗

PubMed2000

Responses of aquatic communities to 25-6 alcohol ethoxylate in model stream ecosystems.

A model stream ecosystem evaluation of the non-commercial alcohol ethoxylate 25-6 alcohol ethoxylate (AE) was performed in 1994. Algal, heterotrophic microbial, protozoan, and invertebrate communities were assessed over an 8-week exposure period that followed an 8-week colonization period. Streams were exposed to nominal concentrations of 0, 12, 37, 111, 333 and 1000 µg AE/l. Confirmed concentrations (8-week means) were 7 (at the detection limit), 13, 36, 76, 259, and 760 µg AE/l as measured at the head of streams on a weekly basis. Microbial communities were initially enhanced by AE exposure (first 2 weeks of exposure), but by the conclusion of the study autotrophic and heterotrophic microbial communities were similar across treatments. In contrast, invertebrate populations and communities responded strongly to AE exposure with adverse effects indicated at 259-760 µg/l by 4 weeks and at 36-760 µg/l by 8 weeks. Key affected groups were the sensitive mayfly, stonefly, and caddisfly fauna. Species richness and abundance of selected populations such as Stenonema (mayfly), Chimarra (caddisfly), and Corbicula (Asiatic clam) were affected. These data indicated a model ecosystem no-observed effect concentration of 13 µg/l for 25-6 AE. In contrast to other published AE model ecosystem studies, 25-6 appears more toxic. Structure-activity-relationships at the model ecosystem level still demonstrate good relationships across a range of surfactants with calculated K(ow)s of 3-6. Importantly, the collective information on fate and effects measured in laboratory and field systems confirms low risk to the environment.

Journal Article↗

PubMed2001

El Niño effects on the dynamics of terrestrial ecosystems.

New studies are showing that the El Niño Southern Oscillation (ENSO) has major implications for the functioning of different ecosystems, ranging from deserts to tropical rain forests. ENSO-induced pulses of enhanced plant productivity can cascade upward through the food web invoking unforeseen feedbacks, and can cause open dryland ecosystems to shift to permanent woodlands. These insights suggest that the predicted change in extreme climatic events resulting from global warming could profoundly alter biodiversity and ecosystem functioning in many regions of the world. Our increasing ability to predict El Niño effects can be used to enhance management strategies for the restoration of degraded ecosystems.

Journal Article↗

PubMed1997

Transport and fate of trifluoroacetate in upland forest and wetland ecosystems.

Although trifluoroacetate (TFA), a breakdown product of chlorofluorocarbon replacements, is being dispersed widely within the biosphere, its ecological fate is largely unknown. TFA was added experimentally to an upland, northern hardwood forest and to a small forest wetland ecosystem within the Hubbard Brook Experimental Forest in New Hampshire. Inputs of TFA were not transported conservatively through these ecosystems; instead, significant amounts of TFA were retained within the vegetation and soil compartments. More TFA was retained by the wetland ecosystem than by the upland forest ecosystem. Using simulation modeling, TFA concentrations were predicted for soil and drainage water until the year 2040.

Adsorption↗

PubMed2004

Self-organization and vegetation collapse in salt marsh ecosystems.

Complexity theory predicts that local feedback processes may strongly affect the organization of ecosystems on larger spatial scales. Whether complexity leads to increased resilience and stability or to increased vulnerability and criticality remains one of the dominant questions in ecology. We present a combined theoretical and empirical study of complex dynamics in mineralogenic salt marsh ecosystems that emerge from a positive feedback between clay accumulation and plant growth. Positive feedback induces self-organizing within the ecosystem, which buffers for the strong physical gradient that characterizes the marine-terrestrial boundary, and improves plant growth along the gradient. However, as a consequence of these self-organizing properties, salt marshes approach a critical state as the edge of the salt marsh and the adjacent intertidal flat becomes increasingly steep and vulnerable to wave attack. Disturbance caused, for instance, by a storm may induce a cascade of vegetation collapse and severe erosion on the cliff edge, leading to salt marsh destruction. Our study shows that on short timescales, self-organization improves the functioning of salt marsh ecosystems. On long timescales, however, self-organization may lead to destruction of salt marsh vegetation.

Biodiversity↗

PubMed1998

The CO2 balance of unproductive aquatic ecosystems

Community respiration (R) rates are scaled as the two-thirds power of the gross primary production (P) rates of aquatic ecosystems, indicating that the role of aquatic biota as carbon dioxide sources or sinks depends on its productivity. Unproductive aquatic ecosystems support a disproportionately higher respiration rate than that of productive aquatic ecosystems, tend to be heterotrophic (R > P), and act as carbon dioxide sources. The average P required for aquatic ecosystems to become autotrophic (P > R) is over an order of magnitude greater for marshes than for the open sea. Although four-fifths of the upper ocean is expected to be net heterotrophic, this carbon demand can be balanced by the excess production over the remaining one-fifth of the ocean.

Journal Article↗

PubMed1965

Basis for the exclusion of Escherichia coli from the rumen ecosystem.

The possible causes for the exclusion of Escherichia coli from the rumen ecosystem were investigated. Evidence presented indicates that oxidation-reduction potential, temperature, pH, CO(2), volatile fatty acids, traces of heavy metals, and bacteriophage are not environmental factors which select against E. coli in the rumen ecosystem. The feeding of nutrients utilizable by E. coli to an artificially inoculated continuous-culture rumen ecosystem did not prevent the washout of the E. coli from the continuous cultures. The presence of an inhibitor of E. coli growth was demonstrated. High concentrations of rumen fluid (50 to 100%) were necessary to inhibit growth in Antibiotic Medium 3. The inhibitor may operate to control the growth of E. coli in the rumen ecosystem. Because of the presence of an inhibitor, the possibility that rumen fluid is deficient in nutrients to support the growth of E. coli cannot be eliminated.

Animals↗

PubMed1976

Model ecosystem evaluation of the environmental impacts of the veterinary drugs phenothiazine, sulfamethazine, clopidol, and diethylstilbestrol.

Four veterinary drugs of dissimilar chemical structures were evaluated for environmental stability and penchant for bioaccumulation. The techniques used were (1) a model aquatic ecosystem (3 days) and (2) a model feedlot ecosystem (33 days) in which the drugs were introduced via the excreta of chicks or mice. The model feedlot ecosystem was supported by metabolism cage studies to determine the amount and the form of the drug excreted by the chicks or mice. Considerable quantities of all the drugs were excreted intact or as environmentally short-lived conjugates. Diethylstilbestrol (DES) and Clopidol were the most persistent molecules, but only DES bioaccumulated to any appreciable degree. Phenothiazine was very biodegradable; sulfamethazine was relatively biodegradable and only accumulated in the organisms to very low levels. Data from the aquatic model ecosystem demonstrated a good correlation between the partition coefficients of the drugs and their accumulation in the fish.

Animals↗

PubMed1994

Estimating the effects of toxicants on ecosystem services.

Numerous functions of ecosystems are essential to the quality of human life, including the provision of food, the decomposition of sewage, the provision of portable water, and the replacement of breathable air. Although attributes of ecosystems directly of use to human societies are not the only ones worth protecting, emphasizing their services may be the most effective means of communicating risks of toxicants to the general public. However, although spatial and temporal scales of experiments to assess risk vary relatively little, actual spatial scales vary considerably, from local environments to global ecosystems. Generally, models are used to bridge these gaps in scale. In this paper, we examine ways in which toxicity test endpoints have been developed to describe effects of pollutants on essential ecosystem functions and the ways in which results are then extrapolated to scales that risk managers can use.

Animals↗

PubMed1996

Mini ecosystem in space--preliminary experiment on board STS-77.

An enclosed ecosystem which is stable on Earth will behave differently when brought into space. Micro-gravity and radiation will affect the dynamics of material circulation or the activities of small creatures of the ecosystem. One series of space experiments aiming to address such issues was planned in the United States (It is termed as ABS--Autonomous Biological System) and Japanese group has been involved with cooperating with the analysis of the flight samples. Before the ecosystem will be on board Russian Space Station "Mir" later 1996 for 3 months, a preliminary flight was carried out in May 1996 on Space Shuttle (STS-77) for 10 days flight. It was the first of such experiments to fly one whole ecosystem in space.

Animals↗

PubMed2003

[Importance of the vaginal ecosystem examination in the first trimester of pregnancy].

OBJECTIVES: Vaginal ecosystem disturbances especially bacterial vaginosis are strongly associated with infectious complication during the course of pregnancy. DESIGN: The aim of the study was the determination of the vaginal ecosystem examination for the diagnosis of the following infection: bacterial vaginosis, candidiasis and trichomoniasis in pregnant women in the first trimester of pregnancy. MATERIALS AND METHODS: The studies included 106 randomly selected asymptomatic pregnant women in I trimester of pregnancy coming for gynaecological examination for the first time after cessation of menstruation were divided into two group: 56 primiparae and 50 multiparae. The diagnosis of BV was based on Amsel criteria concerning vaginal secretion. Trichomonas vaginalis was determined in wet vaginal smear. Candida albicans was detected in vaginal smear after addition of 10% KOH solution. RESULTS: Out of 106 studied subjects in the first trimester of pregnancy, BV was detected in 17.9%, Candida albicans in 15.1%, Trichomonas vaginalis in 3.8%. The detectability of BV infection varied significantly between both groups of studied women (p < 0.001) while no correlation was found between the occurrence of Candida albicans and Trichomonas vaginalis infections. CONCLUSION: Vaginal ecosystem screening in pregnant women makes possible under ambulatory conditions, to detect the following infections: BV, candidiasis and trichomoniasis. Determination of disturbances in vaginal ecosystem is simple and inexpensive, not requiring laboratory facilities for the assessment of vaginal infections.

Adult↗

PubMed2001

Evaluation of pollution-related stress factors for forest ecosystems in central Europe.

Since the early eighties air pollution by SO2 and Pb and, to a lesser degree by NOx and NH3, have been significantly reduced in Europe. This was done in part for the protection of forest ecosystems. The reductions are reflected in the pollutant impacts and inputs and have been verified through the bioindicator Norway spruce. In contrast, ozone concentrations increased at most of the evaluated measuring locations and trends were calculated based on the results of about 100 stations in Austria and Germany. Despite reduced emissions, large parts of the forest ecosystems are still affected by air-pollution impacts. Negative effects can be assessed using different legal standards and Critical Levels and Critical Loads, respectively: The legal standard for the evaluation of SO2 impact, as used in Austria, is well suited. The provisional European Critical Level for ozone, the AOT40 must, in order to be a meaningful criterion for field applications, be further refined. Continuing the Critical Load concept, the spatial risk of acid depositions in areas of high geomorphic variability were evaluated using the new parameter of 'critical soil depth'. With the help of the newly defined 'lead accumulation index', the accumulation of Pb from air pollution could be evaluated. Air-pollution inputs and the spatial acidification risk is directly related to altitude. Up to altitudes of 1000 m and 1100 m, SO2 impact and acid depositions, respectively were indicated and elevated ozone doses and Pb inputs were observed in the sensitive sub-alpine areas. These results underline the necessity for increased protection of mountain forest ecosystems, among others through a further reduction of emissions or forest-related strategies.

Air Pollutants↗

PubMed2006

Cadaver decomposition in terrestrial ecosystems.

A dead mammal (i.e. cadaver) is a high quality resource (narrow carbon:nitrogen ratio, high water content) that releases an intense, localised pulse of carbon and nutrients into the soil upon decomposition. Despite the fact that as much as 5,000 kg of cadaver can be introduced to a square kilometre of terrestrial ecosystem each year, cadaver decomposition remains a neglected microsere. Here we review the processes associated with the introduction of cadaver-derived carbon and nutrients into soil from forensic and ecological settings to show that cadaver decomposition can have a greater, albeit localised, effect on belowground ecology than plant and faecal resources. Cadaveric materials are rapidly introduced to belowground floral and faunal communities, which results in the formation of a highly concentrated island of fertility, or cadaver decomposition island (CDI). CDIs are associated with increased soil microbial biomass, microbial activity (C mineralisation) and nematode abundance. Each CDI is an ephemeral natural disturbance that, in addition to releasing energy and nutrients to the wider ecosystem, acts as a hub by receiving these materials in the form of dead insects, exuvia and puparia, faecal matter (from scavengers, grazers and predators) and feathers (from avian scavengers and predators). As such, CDIs contribute to landscape heterogeneity. Furthermore, CDIs are a specialised habitat for a number of flies, beetles and pioneer vegetation, which enhances biodiversity in terrestrial ecosystems.

Aged↗

PubMed2006

The parasite connection in ecosystems and macroevolution.

In addition to their obvious negative effects ("pathogens"), endoparasites of various kinds play an important role in shaping and maintaining modern animal communities. In the long-term, parasites including pathogens are indispensable entities of any ecosystem. To understand this, it is essential that one changes the viewpoint from the host's interests to that of the parasite. Together with geographic isolation, trophic arms race, symbiosis, and niche partitioning, all parasites (including balance strategists, i.e. seemingly non-pathogenic ones) modulate their hosts' population densities. In addition, heteroxenic parasites control the balance between predator and prey species, particularly if final and intermediate hosts are vertebrates. Thereby, such parasites enhance the bonds in ecosystems and help maintain the status quo. As the links between eukaryotic parasites and their hosts are less flexible than trophic connections, parasite networks probably contributed to the observed stasis and incumbency of ecosystems over geologic time, in spite of continuous Darwinian innovation. Because heteroxenic parasites target taxonomic levels above that of the species (e.g. families), these taxa may have also become units of selection in global catastrophies. Macroevolutionary extrapolations, however, are difficult to verify because endoparasites cannot fossilize.

Animals↗

PubMed2001

Content of metals in compartments of ecosystem of a siberian pond.

During three field seasons (June--September) of 1997--99 contents of Na, K, Ca, Mg, Fe, Mn, Zn, Cu, Al, Cr, Ni, Cd, and Pb were determined in compartments of ecosystem (surrounding soils, bottom sediments, water, zoobenthos, macrophytes, and fish) of a fish and recreation pond situated at the edge of Krasnoyarsk City (Siberia, Russia). Contents of most parts of metals in soils, water, and macrophytes significantly correlated with each other. As concluded, their contents were determined by natural, general, geochemical peculiarities of the region. Heavy metals, contents of which were higher than federal upper limits of concentration, were revealed. In muscles of fish with different feeding spectra--crucian and perch--concentrations of some metals differed significantly; correlation graphs for metals also had different structures. Comparison of our data with those on diverse aquatic ecosystems of Siberia, Europe, North America, and China published in the last decade was carried out. It was concluded that a distribution of heavy metals in the compartments of an aquatic ecosystem presently have to be determined for each particular water body until general regularities are discovered.

Animals↗

PubMed2006

Salmonella spp., Vibrio spp., Clostridium perfringens, and Plesiomonas shigelloides in marine and freshwater invertebrates from coastal California ecosystems.

The coastal ecosystems of California are highly utilized by humans and animals, but the ecology of fecal bacteria at the land-sea interface is not well understood. This study evaluated the distribution of potentially pathogenic bacteria in invertebrates from linked marine, estuarine, and freshwater ecosystems in central California. A variety of filter-feeding clams, mussels, worms, and crab tissues were selectively cultured for Salmonella spp., Campylobacter spp., Escherichia coli-O157, Clostridium perfringens, Plesiomonas shigelloides, and Vibrio spp. A longitudinal study assessed environmental risk factors for detecting these bacterial species in sentinel mussel batches. Putative risk factors included mussel collection near higher risk areas for livestock or human sewage exposure, adjacent human population density, season, recent precipitation, water temperature, water type, bivalve type, and freshwater outflow exposure. Bacteria detected in invertebrates included Salmonella spp., C. perfringens, P. shigelloides, Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio alginolyticus. Overall, 80% of mussel batches were culture positive for at least one of the bacterial species, although the pathogens Campylobacter, E. coli-O157, and Salmonella were not detected. Many of the same bacterial species were also cultured from upstream estuarine and riverine invertebrates. Exposure to human sewage sources, recent precipitation, and water temperature were significant risk factors for bacterial detection in sentinel mussel batches. These findings are consistent with the hypothesis that filter-feeding invertebrates along the coast concentrate fecal bacteria flowing from land to sea and show that the relationships between anthropogenic effects on coastal ecosystems and the environmental niches of fecal bacteria are complex and dynamic.

Animals↗

PubMed2004

Microbial characterization of toluene-degrading denitrifying consortia obtained from terrestrial and marine ecosystems.

The degradation characteristics of toluene coupled to nitrate reduction were investigated in enrichment culture and the microbial communities of toluene-degrading denitrifying consortia were characterized by denaturing gradient gel electrophoresis (DGGE) technique. Anaerobic nitrate-reducing bacteria were enriched from oil-contaminated soil samples collected from terrestrial (rice field) and marine (tidal flat) ecosystems. Enriched consortia degraded toluene in the presence of nitrate as a terminal electron acceptor. The degradation rate of toluene was affected by the initial substrate concentration and co-existence of other hydrocarbons. The types of toluene-degrading denitrifying consortia depended on the type of ecosystem. The clone RS-7 obtained from the enriched consortium of the rice field was most closely related to a toluene-degrading and denitrifying bacterium, Azoarcus denitrificians (A. tolulyticus sp. nov.). The clone TS-11 detected in the tidal flat enriched consortium was affiliated to Thauera sp. strain S2 (T. aminoaromatica sp. nov.) that was able to degrade toluene under denitrifying conditions. This indicates that environmental factors greatly influence microbial communities obtained from terrestrial (rice field) and marine (tidal flat) ecosystems.

Anaerobiosis↗